Top View of Binary Tree in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new node with given value.

DSA Javascript

class Node {
  constructor(data) {
    this.data = data;
    this.left = null;
    this.right = null;
  }
}

const root = new Node([1]);

Drag options to blanks, or click blank then click option'

Anull

B10

C'root'

Dundefined

Attempts:

3 left

💡 Hint

Common Mistakes

Using null or undefined as node data

Using a string instead of a number

The root node should be created with the value 10 as data.

2fill in blank

medium

Complete the code to add a left child node to the root.

DSA Javascript

root.left = new Node([1]);

Drag options to blanks, or click blank then click option'

A5

Bnull

C'left'

Dundefined

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning null or undefined instead of a node

Using a string instead of a number

The left child node should have the value 5.

3fill in blank

hard

Fix the error in the function to calculate the top view horizontal distance.

DSA Javascript

function topView(root) {
  const map = new Map();
  const queue = [];
  queue.push({ node: root, hd: [1] });
  // hd means horizontal distance
}

Drag options to blanks, or click blank then click option'

A1

B-1

C0

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Starting horizontal distance at 1 or -1

Using null instead of a number

The horizontal distance of the root node is 0 by definition.

4fill in blank

hard

Fill both blanks to correctly update the horizontal distance for left and right children.

DSA Javascript

while (queue.length > 0) {
  const { node, hd } = queue.shift();
  if (!map.has(hd)) {
    map.set(hd, node.data);
  }
  if (node.left) queue.push({ node: node.left, hd: hd [1] 1 });
  if (node.right) queue.push({ node: node.right, hd: hd [2] 1 });
}

Drag options to blanks, or click blank then click option'

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition for left child

Using multiplication or division instead of addition/subtraction

Left child horizontal distance is parent's hd minus 1, right child is parent's hd plus 1.

5fill in blank

hard

Fill all three blanks to create the final top view array from the map.

DSA Javascript

const sortedKeys = Array.from(map.keys()).sort((a, b) => a [1] b);
const topViewArr = sortedKeys.map(key => map.get(key));
return topViewArr; // returns array of node.data in top view order

Drag options to blanks, or click blank then click option'

A-

B>

C<

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' which sorts in descending order

Using '+' which is arithmetic, not comparison

Sorting keys in ascending order requires comparing with '-' to order properly.